Nothing lives forever, not even the stars. Our Sun, like all true stars, thrives on nuclear fusion in its core.

A star reaching the end of its life goes from fusing nuclei to blowing off its outer layers and contracting down. Image credit: NASA, ESA, and A. Zijlstra (The University of Manchester); Acknowledgment: J. Barrington (Hubble's Hidden Treasures Competition).

At millions of degrees, it converts hydrogen into helium, and will later heat up further, fusing helium into carbon.

The gaseous outer layers of a Sun-like star glow in space after being expelled as the star reached the end of its life.Image credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA).

Like most stars, it will never get hot enough to go supernova. When it runs out of fuel, it will contract into a white dwarf, blowing off its outer layers, forming a planetary nebula.

The planetary nebula NGC 6369's blue-green ring marks the location where energetic ultraviolet light has stripped electrons from oxygen atoms in the gas. Image credit: NASA and The Hubble Heritage Team (STScI/AURA).

This example of cosmic recycling will send both hydrogen and heavier elements back into the interstellar medium.

Stars up to 800% the mass of the Sun will achieve this fate, with planetary nebulae taking on a variety of morphologies.

Four individual planetary nebulae -- He 2-47, NGC 5315, IC 4593, and NGC 5307 -- were imaged by Hubble in February of 2007. Image credit: NASA, ESA, and The Hubble Heritage Team (STScI/AURA).

Single stars may blow off their outer layers spherically, like 20% of planetary nebulae.

The Eight Burst Nebula, NGC 3132, is not well-understood in terms of its shape or formation. The different colors in this image represent different temperatures. Image credit: The Hubble Heritage Team (STScI/AURA/NASA).

Stars with binary companions may produce spirals or other asymmetrical shapes.

Mostly Mute Monday tells the story of a single astronomical phenomenon or object primarily in visuals, with no more than 200 words of text.

I am a Ph.D. astrophysicist, author, and science communicator, who professes physics and astronomy at various colleges. I have won numerous awards for science writing since 2008 for my blog, Starts With A Bang, inclu...